1. Field of the Invention
The present invention relates to an information distributor (a so-called server) in which information is stored, and upon receipt of information distributing request, the requested information is distributed toward an information distribution demand source, an information display apparatus (a so-called client) in which information distribution is requested to an information distribution source, and information provided from the information distribution source is displayed on a display screen, and an information display system in which the information distributor and the information display apparatus are connected via communication lines to one another.
2. Description of the Related Art
Information display systems as mentioned above, that is, systems in which the server and the client are connected via communication lines such as a telephone line, a LAN and the like, have come into wide use recently.
FIG. 21 is a block diagram showing the basic arrangement of constituents of a network system having a server and a client. Usually, while there is a case in which a plurality of clients are connected and also a plurality of servers are connected, here it is assumed, for the purpose of simplification, that one server and one client are connected to one another through a network.
FIG. 22(A) and 22(B) are each a typical illustration of a format of information stored in a server.
The server 10 is provided with a large capacity of information storage unit 11. The information storage unit 11, stored much information, such as a non-compressed type of information, as shown in FIG. 22 (A), which can be displayed as it is, and a compression type of information, as shown in FIG. 22 (B), which cannot be displayed as proper information in the present form. An advantageous point of storage of information in compressed form resides in the point that a data storage capacity can be reduced. On the other hand, in order to display such information as proper information, there is a need to expand the compression type of information into the non-compressed type of information.
The server 10 further comprises a computer 12, such as a personal computer (PC) and a work station (WS), for executing programs to operate the server 10 including a program for accessing the information storage unit 11 and a program for transmitting the information read from the information storage unit 11 via a network 30 to the client; and display 13 for displaying information involved in management of the server 10.
The server 10 basically has the arrangement as mentioned above, and serves to distribute information via the network 30 to the client 20.
Specifically, as a famous server system, there is known a WWW (World Wide Web) of an interest. Usually, actuation of an HTTP daemon on an OS (Operating System) such as an UNIX or Windows NT permits access from a client application such as Mosaic, thereby transmitting information of interest to the client.
On the other hand, the client 20 is a computer system having a display 21 for displaying information transmitted from the server 10. The client 20 comprises an interface 22 for receiving and transmitting data via the network 30; a CPU 23 for executing an OS, an application software and the like; a memory 24 for temporarily storing the OS, the application software and various kinds of data so that the CPU 23 may refer to those; an information storage unit 25 for storing the OS, the application software, data and the like; and a user interface 26 including a keyboard, a mouse and the like. The information storage unit 25 comprises, usually, a hard disk device and the like so as to store an application software for expanding a compression type of data, an application software for an information display, and the like. Those application softwares are developed on the memory 24 when executed in the CPU 23. The information storage unit 25 serves as a storage place for temporarily storing information transferred from the server 10.
The client 20 has basically a structure of usual personal computer as mentioned above. For example, a WWW browser (an example of a communication software) such as Mosaic is available. The client 20 is operative to request a distribution of information through the network 30 to the server 10 and to display on the display 21 information transmitted from the server 10 via the network 30. It is possible, through clicking by the mouse provided as the user interface 26, of the information displayed on the display 21 characters or still picture portions linked with other information, to display the linked information.
FIG. 23 is a flowchart showing schematically a basic processing routine in the server and the client.
First, at the client end the communication software is activated (step 20-1), and information to be displayed is requested to the server (step 20-2). At the server end, it is observed as to whether information distribution demand has been received from the client (step 10-1). When the server received the information distribution demand from the client, the server transmits the requested information (file) to the client (step 10-2). The client refers to a header of the transmitted file to determine as to whether the transmitted file is a compressed type of file or a non-compressed type of file (step 20-3) on a basis of information recorded on the header. In a case where it is the non-compressed type of file, upon receipt of the information in its entirety (step 20-4), the information is displayed (step 20-5).
In step 20-3, when it is determined that the file transmitted from the server is an information file of a compressed type, the process goes to step 20-6 in which it is determined whether the provided file is to be preserved. The reason why it is determined whether the file is to be preserved is that in case of the compressed file, it takes a lot of time to expand the compressed file, or there is a need to additionally provide a corresponding expansion software, and in view of the foregoing, it often happens that the file is cancelled without being displayed. It is acceptable that such a decision is effected through operation of the user interface 26 by a user of the client, alternately it is instructed beforehand to the client that the compressed file is not preserved. In a case where the compressed file is to be preserved, after completion of receiving of the compressed file (step 20-7), the received information is stored in form of compression in the information storage unit 25 (step 20-8).
After the preservation, an information expansion program is activated so that the compressed file stored in the information storage unit 25 is expanded into the form of non-compression and displayed on the display 21.
In the system, as mentioned above, in which information is transmitted from the server to the client and the transmitted information is displayed at the client end, it is desired that after the client requires the server to provide information, the required information is transmitted in short time from the server and is immediately displayed.
However, in case of non-compressed type of information, it takes a lot of time to transmit information from the server 10 to the client 20. Specifically, in a case where a communication rate of the network 30 is low, or in a case where information, which is large in information rate, for example, information of images or animations, is transmitted, it takes a lot of time before that information is displayed. This involves a problem such that the user of the client 20 is obliged to wait such long time. Further, in a case where the network 30 is a telephone line, taking much time for communication involves a problem such that a service charge for use of the line is increased. Furthermore, in a case where an internet is utilized, a line-occupied factor will be increased. This brings about a problem such that an increment of the user involves a lowering of the transfer rate.
On the other hand, in a case where the compressed type of information is transferred from the server 10 to the client 20, the communication time is reduced by the corresponding reduced data capacity in which information is compressed. However, at the client end which receives the compressed information, there is a need to expand the compressed information to the non-compressed type of information. Thus, it takes much time for expansion. Also in this case, there arises a problem such that it takes a lot of time before information is displayed.
FIGS. 24 (A) and (B) are each a typical illustration useful for understanding a display scheme for a GIF type of image information.
As to the GIF type of image information, there is known a scheme in which as shown in FIG. 24 (B), an image is displayed in the order of scan lines 1, 2, 3, . . . arranged on a jumping basis, a so-called interlace reproducing is performed, instead of a scheme in which as shown in FIG. 24 (A), an image is displayed in the order of scan lines 1, 2, 3, . . . arranged on a sequential basis. Also in case of the interlace reproducing, the total time taken up to a sheet of picture being displayed in its entirety is the same as the scheme shown in FIG. 24 (A). In spite of this matter, the interlace reproducing scheme may give the impression for the user of the client 20 just like that the image is displayed in short time after the user requests information. Thus, the user of the client 20 may be released from an irritation such that the user is obliged to wait for a long time before the image is displayed. However, this scheme is applicable to the GIF type of image only, but not applied to another file type of information. Further, it is noted that the interlace reproducing scheme simply gives the user of the client 20 an illusion just like that the image is immediately displayed, but the display of information is not indeed hastened.